Gigantochloa balui

Gigantochloa balui K.M. Wong

For. Dept. Occ. Pap., Brun. 1: 1-10 (1990).
2n = unknown

Origin and geographic distribution
The origin of G. balui is still uncertain but could possibly be in Indo-China; several collections from southern Thailand, which appear to be this species and which have been taken from plants growing wild, have been made. This bamboo is always found in association with settlements in Sabah, Sarawak (Malaysia), Brunei and West Kalimantan (Indonesia) but has never been noted in situations where it might be truly considered wild. For map click: Map419.TIF. It thus appears to have been introduced to Borneo.

G. balui is cultivated in many villages in Sabah, Sarawak and Brunei for its useful culms. In Brunei, the culms are used as poles and split for plaiting baskets. In Sabah, the culms have been reportedly used as fishing stakes, sailing masts and for framing, in addition to being used in the split form for basketry. In Sarawak, the culm internodes have been used for cooking meat and vegetables, and for making handicrafts. In West Kalimantan (Indonesia) the culms are used for building structures (walls, floorings) and traditional basketry. The young shoots are reported as edible in Sabah and Brunei, but this is not a popular or extensive use of the species. The young shoots of G. levis (Blanco) Merrill (in Borneo and the Philippines) and Dendrocalamus asper (Schultes f.) Backer ex Heyne, for instance, are much preferred to those of G. balui.

Densely tufted sympodial bamboo. Culm erect, slightly arching outwards, up to 12 m tall, diameter 3-8 cm near the base, plain green or white or pale yellow stripes at the base; internodes non-waxy, up to 40 cm long, covered with appressed pale silver hairs; nodes not conspicuously swollen. Branch complement at each midculm node arising from a single bud, consisting of a dominant primary branch, 1-2 subdominant branches from its base and several lesser branchlets of higher orders. Culm sheath pale green, sometimes with faint yellow stripes, covered with appressed pale silver hairs; blade broadly triangular on lower sheaths, broadly lanceolate on midculm and upper sheaths, green or sometimes flushed purple, spreading to reflexed; ligule lacerate, the base 1-3 mm long, the lacerations to 4 mm long; auricles low and rimlike, up to about 2.5 mm tall, glabrous, dark green to dark purple. Leaf blade 20-35 cm x 2-4 cm, lower surface slightly glaucous and hairy; ligule a low glabrous rim to c. 1 mm long; auricles small rounded glabrous lobes to c. 1 mm long. Inflorescences borne on branches of leafy or leafless culms, bearing groups of 3-10 pseudospikelets at each node; pseudospikelet 9-12 mm long, with 3-5 glumes, 2-3 perfect florets and a vestigial terminal floret represented by an empty lemma 9-10 mm long. Caryopsis unknown.

Growth and development
No information exists from systematically observed populations. In a trial plot of G. balui at Sungai Daling, Sandakan, Sabah, Malaysia, observed in 1992 at eight years after planting from cuttings, the number of healthy mature culms per clump was estimated at 20-40. Further development is being monitored by the Forest Research Centre at Sepilok, Sandakan.
Flowering clumps are not commonly encountered, which is probably a major reason why the botanical identity of G. balui eluded workers for a long time. However, when a clump does flower, most or all culms gradually become generative, and an entire flowering episode can last up to a whole year. One clump observed in Brunei Darussalam flowered during a period of 14 months, followed by new regeneration from the rhizome system.

Other botanical information
The presence of pale silver hairs on the culm sheaths and internodes, and the glabrous rim-like culm-sheath auricles allow rapid identification of G. balui in the field.

G. balui appears to grow best on rich alluvial sites, especially near rivers, and also establishes well in secondary forest. In dense groves of G. balui documented in Brunei Darussalam it grows in tight clumps to the exclusion of most other plants. This is partly due to the accumulation of much siliceous leaf litter on the ground, which decays only slowly and prevents effective establishment of other plants.

Propagation and planting
Rhizome cuttings (offsets) and culm cuttings can be used quite effectively to propagate clones of G. balui. In Sabah, the use of culm cuttings taken from mature, but not senescent culms guarantees a high degree of success in producing new plants in 3-4 months, provided water is not limiting. Rooted cuttings with several leafy branches can be planted out in the field, in holes into which manure and fertilizer have been put. Preliminary observations of a trial in Sandakan, Sabah, indicate that a distance of 4-6 m between individual clumps facilitates optimum growth and minimizes weed problems.

Diseases and pests
So far, no serious diseases have been observed in G. balui. Even witches' broom disease, common in cultivated G. levis in Brunei, has not been observed thus far.

Only mature culms, 2 or more years old, are being harvested. In West Kalimantan 1-year-old culms are preferred for basketry.

Genetic resources and breeding
There are no germplasm collections of G. balui. If indeed G. balui has been introduced to Borneo from mainland Asia, then the genetic base of the populations established in northern and western Borneo is likely to be a narrow one. A germplasm collection with representatives from all growing areas could widen the base for selection and breeding purposes.

There is potential for G. balui as a plantation crop for bamboo-shoot and culm production. This can only be pursued with the appropriate pilot-scale investigations into aspects of the establishment, growth and development and management of this bamboo.

K.M. Wong

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